Conventionally, sensor apparatuses including a multi-optical-axis photoelectric sensor have been used as sensor apparatuses for sensing a sensing target in various types of manufacturing equipment.
An ordinary multi-optical-axis photoelectric sensor includes a light projecting unit in which multiple light emitting elements are arranged linearly, and a light receiving unit in which the same number of light receiving elements as the light emitting elements are arranged linearly, and the light emitting elements and light receiving elements are arranged so as to face each other in a one-to-one relationship. Also, the light projecting unit and the light receiving unit are generally synchronized using communication. The light emitting elements are caused to sequentially emit light on the light projecting unit side, and received amounts of light at timings synchronized with the light emission operations of the light emitting elements are acquired from the light receiving elements corresponding to the light emitting elements on light receiving unit side. Accordingly, blocked states of each optical axis of the multi-optical-axis photoelectric sensor are detected in sequence.
Also, a muting function of temporarily disabling an emergency stop function of the manufacturing equipment when a predetermined condition is satisfied has conventionally been used as a function for achieving both safety and productivity at production sites.
FIG. 18 is a diagram for illustrating an example of a conventional sensor apparatus 100 that includes a hazard sensing sensor (multi-optical-axis photoelectric sensor) and a muting sensor (single-optical-axis sensor).
The sensor apparatus 100 shown in the drawing includes a hazard sensing sensor 101, display lamps 102a and 102b, and muting sensors (single-optical-axis sensors) 103 to 106.
The hazard sensing sensor 101 includes a light projecting unit 101a in which multiple light emitting elements are arranged linearly, and a light receiving unit 101b in which the same number of light receiving elements as the light emitting elements are arranged linearly, and the light emitting elements and the light receiving elements are arranged on opposite sides of a conveyance apparatus C conveying a work piece W, and face each other in a one-to-one relationship. Also, a safety function (e.g., an emergency stop function) is activated when the hazard sensing sensor 101 senses an object.
The muting sensors 103 to 106 are arranged upstream and downstream of the hazard sensing sensor 101 in the conveyance direction of the work piece W at a predetermined interval, and signals therefrom are input to the hazard sensing sensor 101. Also, if the sensing result of the muting sensors 103 to 106 satisfies a sensing condition set in advance according to the size, shape, conveyance interval, and the like of the work piece W, a muting function of disabling the emergency stop function of the manufacturing equipment is executed.
Note that in general, the muting function is disabled only while multiple independent muting signals (signals of single-optical-axis sensors, etc.) continue to be input in a predetermined sequence. Also, in the interest of safety, there is a need for an arrangement where the muting signal actually detects the work piece. For this reason, the stability of the muting function largely depends on the performance and stability of the muting signals from the external devices (single-optical-axis sensors, etc.).
Also, EP 2037297B discloses that a multi-optical-axis photoelectric sensor is arranged in a horizontal direction (arranged so that light emitting elements and light receiving elements are aligned along the conveyance direction of a work piece), and the work piece is sensed according to the result of the multi-optical-axis photoelectric sensor receiving light.
EP 2037297B is an example of background art.